SUPPLEMENTAL CONSOLIDATED FINANCIAL STATEMENT INFORMATION (Details) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) segment	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Number of business segments \| segment			1
Operating revenues	$ 36,976	$ 40,448	$ 112,216	$ 126,486
Deferred cost					$ 6,994	$ 2,991
Deferred costs incurred to fulfill contracts with customers	3,157	7,001	3,157	7,001
Total deferred costs amortized	6,806	14,757	27,253	29,004
Deferred costs impairment losses	0	0	0	0
Deferred revenue	7,970	2,779	7,970	2,779	$ 10,501	$ 6,314
Revenue recognized that was included in deferred revenue balances at beginning of period	427	634	8,604	5,945
United States
Operating revenues	36,814	39,950	96,496	113,015
Canada
Operating revenues	$ 162	$ 498	$ 15,720	$ 13,471

Amount of amortization expense for asset recognized from cost incurred to obtain or fulfill contract with customer.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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